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<!DOCTYPE erlref SYSTEM "erlref.dtd">
<erlref>
<header>
<copyright>
<year>2001</year>
<year>2015</year>
<holder>Ericsson AB, All Rights Reserved</holder>
</copyright>
<legalnotice>
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
The Initial Developer of the Original Code is Ericsson AB.
</legalnotice>
<title>cover</title>
<prepared></prepared>
<docno></docno>
<date></date>
<rev></rev>
</header>
<module>cover</module>
<modulesummary>A Coverage Analysis Tool for Erlang</modulesummary>
<description>
<p>The module <c>cover</c> provides a set of functions for coverage
analysis of Erlang programs, counting how many times each
<em>executable line</em> of code is executed when a program is run. <br></br>
An executable line contains an Erlang expression such as a matching
or a function call. A blank line or a line containing a comment,
function head or pattern in a <c>case</c>- or <c>receive</c> statement
is not executable.</p>
<p>Coverage analysis can be used to verify test cases, making sure all
relevant code is covered, and may also be helpful when looking for
bottlenecks in the code.</p>
<p>Before any analysis can take place, the involved modules must be
<em>Cover compiled</em>. This means that some extra information is
added to the module before it is compiled into a binary which then
is loaded. The source file of the module is not affected and no
<c>.beam</c> file is created.</p>
<p>Each time a function in a Cover compiled module is called,
information about the call is added to an internal database of Cover.
The coverage analysis is performed by examining the contents of
the Cover database. The output <c>Answer</c> is determined by two
parameters, <c>Level</c> and <c>Analysis</c>.</p>
<list type="bulleted">
<item>
<p><c>Level = module</c></p>
<p><c>Answer = {Module,Value}</c>, where <c>Module</c> is the module
name.</p>
</item>
<item>
<p><c>Level = function</c></p>
<p><c>Answer = [{Function,Value}]</c>, one tuple for each function in
the module. A function is specified by its module name <c>M</c>,
function name <c>F</c> and arity <c>A</c> as a tuple
<c>{M,F,A}</c>.</p>
</item>
<item>
<p><c>Level = clause</c></p>
<p><c>Answer = [{Clause,Value}]</c>, one tuple for each clause in
the module. A clause is specified by its module name <c>M</c>,
function name <c>F</c>, arity <c>A</c> and position in the function
definition <c>C</c> as a tuple <c>{M,F,A,C}</c>.</p>
</item>
<item>
<p><c>Level = line</c></p>
<p><c>Answer = [{Line,Value}]</c>, one tuple for each executable
line in the module. A line is specified by its module name <c>M</c>
and line number in the source file <c>N</c> as a tuple
<c>{M,N}</c>.</p>
</item>
<item>
<p><c>Analysis = coverage</c></p>
<p><c>Value = {Cov,NotCov}</c> where <c>Cov</c> is the number of
executable lines in the module, function, clause or line that have
been executed at least once and <c>NotCov</c> is the number of
executable lines that have not been executed.</p>
</item>
<item>
<p><c>Analysis = calls</c></p>
<p><c>Value = Calls</c> which is the number of times the module,
function, or clause has been called. In the case of line level
analysis, <c>Calls</c> is the number of times the line has been
executed.</p>
</item>
</list>
<p><em>Distribution</em></p>
<p>Cover can be used in a distributed Erlang system. One of the
nodes in the system must then be selected as the <em>main node</em>, and all Cover commands must be executed from this
node. The error reason <c>not_main_node</c> is returned if an
interface function is called on one of the remote nodes.</p>
<p>Use <c>cover:start/1</c> and <c>cover:stop/1</c> to add or
remove nodes. The same Cover compiled code will be loaded on each
node, and analysis will collect and sum up coverage data results
from all nodes.</p>
<p>To only collect data from remote nodes without stopping
<c>cover</c> on those nodes, use <c>cover:flush/1</c></p>
<p>If the connection to a remote node goes down, the main node
will mark it as lost. If the node comes back it will be added
again. If the remote node was alive during the disconnected
periode, cover data from before and during this periode will be
included in the analysis.</p>
</description>
<funcs>
<func>
<name>start() -> {ok,Pid} | {error,Reason}</name>
<fsummary>Start Cover.</fsummary>
<type>
<v>Pid = pid()</v>
<v>Reason = {already_started,Pid}</v>
</type>
<desc>
<p>Starts the Cover server which owns the Cover internal database.
This function is called automatically by the other functions in
the module.</p>
</desc>
</func>
<func>
<name>start(Nodes) -> {ok,StartedNodes} | {error,not_main_node}</name>
<fsummary>Start Cover on remote nodes.</fsummary>
<type>
<v>Nodes = StartedNodes = [atom()]</v>
</type>
<desc>
<p>Starts a Cover server on the each of given nodes, and loads
all cover compiled modules.</p>
</desc>
</func>
<func>
<name>compile(ModFiles) -> Result | [Result]</name>
<name>compile(ModFiles, Options) -> Result | [Result]</name>
<name>compile_module(ModFiles) -> Result | [Result]</name>
<name>compile_module(ModFiles, Options) -> Result | [Result]</name>
<fsummary>Compile one or more modules for Cover analysis.</fsummary>
<type>
<v>ModFiles = ModFile | [ModFile]</v>
<v>ModFile = Module | File</v>
<v> Module = atom()</v>
<v> File = string()</v>
<v>Options = [Option]</v>
<v> Option = {i,Dir} | {d,Macro} | {d,Macro,Value} | export_all</v>
<d>See <c>compile:file/2.</c></d>
<v>Result = {ok,Module} | {error,File} | {error,not_main_node}</v>
</type>
<desc>
<p>Compiles a module for Cover analysis. The module is given by its
module name <c>Module</c> or by its file name <c>File</c>.
The <c>.erl</c> extension may be omitted. If the module is
located in another directory, the path has to be specified.</p>
<p><c>Options</c> is a list of compiler options which defaults to
<c>[]</c>. Only options defining include file directories and
macros are passed to <c>compile:file/2</c>, everything else is
ignored.</p>
<p>If the module is successfully Cover compiled, the function
returns <c>{ok,Module}</c>. Otherwise the function returns
<c>{error,File}</c>. Errors and warnings are printed as they
occur.</p>
<p>If a list of <c>ModFiles</c> is given as input, a list
of <c>Result</c> will be returned. The order of the returned
list is undefined.</p>
<p>Note that the internal database is (re-)initiated during
the compilation, meaning any previously collected coverage data
for the module will be lost.</p>
</desc>
</func>
<func>
<name>compile_directory() -> [Result] | {error,Reason}</name>
<name>compile_directory(Dir) -> [Result] | {error,Reason}</name>
<name>compile_directory(Dir, Options) -> [Result] | {error,Reason}</name>
<fsummary>Compile all modules in a directory for Cover analysis.</fsummary>
<type>
<v>Dir = string()</v>
<v>Options = [Option]</v>
<d>See <c>compile_module/1,2</c></d>
<v>Result = {ok,Module} | {error,File} | {error,not_main_node}</v>
<d>See <c>compile_module/1,2</c></d>
<v>Reason = eacces | enoent</v>
</type>
<desc>
<p>Compiles all modules (<c>.erl</c> files) in a directory
<c>Dir</c> for Cover analysis the same way as
<c>compile_module/1,2</c> and returns a list with the return
values.</p>
<p><c>Dir</c> defaults to the current working directory.</p>
<p>The function returns <c>{error,eacces}</c> if the directory is not
readable or <c>{error,enoent}</c> if the directory does not exist.</p>
</desc>
</func>
<func>
<name>compile_beam(ModFiles) -> Result | [Result]</name>
<fsummary>Compile one or more modules for Cover analysis, using existing beam(s).</fsummary>
<type>
<v>ModFiles = ModFile | [ModFile]</v>
<v>ModFile = Module | BeamFile</v>
<v> Module = atom()</v>
<v> BeamFile = string()</v>
<v>Result = {ok,Module} | {error,BeamFile} | {error,Reason}</v>
<v> Reason = non_existing | {no_abstract_code,BeamFile} | {encrypted_abstract_code,BeamFile} | {already_cover_compiled,no_beam_found,Module} | not_main_node</v>
</type>
<desc>
<p>Does the same as <c>compile/1,2</c>, but uses an existing
<c>.beam</c> file as base, i.e. the module is not compiled
from source. Thus <c>compile_beam/1</c> is faster than
<c>compile/1,2</c>.</p>
<p>Note that the existing <c>.beam</c> file must contain
<em>abstract code</em>, i.e. it must have been compiled with
the <c>debug_info</c> option. If not, the error reason
<c>{no_abstract_code,BeamFile}</c> is returned.
If the abstract code is encrypted, and no key is available
for decrypting it, the error reason
<c>{encrypted_abstract_code,BeamFile}</c> is returned.</p>
<p>If only the module name (i.e. not the full name of the
<c>.beam</c> file) is given to this function, the
<c>.beam</c> file is found by calling
<c>code:which(Module)</c>. If no <c>.beam</c> file is found,
the error reason <c>non_existing</c> is returned. If the
module is already cover compiled with <c>compile_beam/1</c>,
the <c>.beam</c> file will be picked from the same location
as the first time it was compiled. If the module is already
cover compiled with <c>compile/1,2</c>, there is no way to
find the correct <c>.beam</c> file, so the error reason
<c>{already_cover_compiled,no_beam_found,Module}</c> is
returned.</p>
<p><c>{error,BeamFile}</c> is returned if the compiled code
can not be loaded on the node.</p>
<p>If a list of <c>ModFiles</c> is given as input, a list
of <c>Result</c> will be returned. The order of the returned
list is undefined.</p>
</desc>
</func>
<func>
<name>compile_beam_directory() -> [Result] | {error,Reason}</name>
<name>compile_beam_directory(Dir) -> [Result] | {error,Reason}</name>
<fsummary>Compile all .beam files in a directory for Cover analysis.</fsummary>
<type>
<v>Dir = string()</v>
<v>Result = See compile_beam/1</v>
<v>Reason = eacces | enoent</v>
</type>
<desc>
<p>Compiles all modules (<c>.beam</c> files) in a directory
<c>Dir</c> for Cover analysis the same way as
<c>compile_beam/1</c> and returns a list with the return
values.</p>
<p><c>Dir</c> defaults to the current working directory.</p>
<p>The function returns <c>{error,eacces}</c> if the directory is not
readable or <c>{error,enoent}</c> if the directory does not exist.</p>
</desc>
</func>
<func>
<name since="OTP 18.0">analyse() -> {result,Ok,Fail} | {error,not_main_node}</name>
<name>analyse(Modules) -> OneResult | {result,Ok,Fail} | {error,not_main_node}</name>
<name>analyse(Analysis) -> {result,Ok,Fail} | {error,not_main_node}</name>
<name>analyse(Level) -> {result,Ok,Fail} | {error,not_main_node}</name>
<name>analyse(Modules, Analysis) -> OneResult | {result,Ok,Fail} | {error,not_main_node}</name>
<name>analyse(Modules, Level) -> OneResult | {result,Ok,Fail} | {error,not_main_node}</name>
<name>analyse(Analysis, Level) -> {result,Ok,Fail} | {error,not_main_node}</name>
<name>analyse(Modules, Analysis, Level) -> OneResult | {result,Ok,Fail} | {error,not_main_node}</name>
<fsummary>Analyse one or more Cover compiled modules.</fsummary>
<type>
<v>Modules = Module | [Module]</v>
<v>Module = atom() </v>
<v>Analysis = coverage | calls</v>
<v>Level = line | clause | function | module</v>
<v>OneResult = {ok,{Module,Value}} | {ok,[{Item,Value}]} | {error, Error}</v>
<v> Item = Line | Clause | Function</v>
<v> Line = {M,N}</v>
<v> Clause = {M,F,A,C}</v>
<v> Function = {M,F,A}</v>
<v> M = F = atom()</v>
<v> N = A = C = integer()</v>
<v> Value = {Cov,NotCov} | Calls</v>
<v> Cov = NotCov = Calls = integer()</v>
<v> Error = {not_cover_compiled,Module}</v>
<v>Ok = [{Module,Value}] | [{Item,Value}]</v>
<v>Fail = [Error]</v>
</type>
<desc>
<p>Performs analysis of one or more Cover compiled modules, as
specified by <c>Analysis</c> and <c>Level</c> (see above), by
examining the contents of the internal database.</p>
<p><c>Analysis</c> defaults to <c>coverage</c> and <c>Level</c>
defaults to <c>function</c>.</p>
<p>If <c>Modules</c> is an atom (one module), the return will
be <c>OneResult</c>, else the return will be
<c>{result,Ok,Fail}</c>.</p>
<p>If <c>Modules</c> is not given, all modules that have data
in the cover data table, are analysed. Note that this
includes both cover compiled modules and imported
modules.</p>
<p>If a given module is not Cover compiled, this is indicated
by the error reason <c>{not_cover_compiled,Module}</c>.</p>
</desc>
</func>
<func>
<name since="OTP 18.0">analyse_to_file() -> {result,Ok,Fail} | {error,not_main_node}</name>
<name>analyse_to_file(Modules) -> Answer | {result,Ok,Fail} | {error,not_main_node}</name>
<name>analyse_to_file(Options) -> {result,Ok,Fail} | {error,not_main_node}</name>
<name>analyse_to_file(Modules,Options) -> Answer | {result,Ok,Fail} | {error,not_main_node}</name>
<fsummary>Detailed coverage analysis of one or more Cover compiled modules.</fsummary>
<type>
<v>Modules = Module | [Module]</v>
<v>Module = atom()</v>
<v>OutFile = OutDir = string()</v>
<v>Options = [Option]</v>
<v>Option = html | {outfile,OutFile} | {outdir,OutDir}</v>
<v>Answer = {ok,OutFile} | {error,Error}</v>
<v>Ok = [OutFile]</v>
<v>Fail = [Error]</v>
<v>Error = {not_cover_compiled,Module} | {file,File,Reason} | {no_source_code_found,Module}</v>
<v> File = string()</v>
<v> Reason = term()</v>
</type>
<desc>
<p>Makes copies of the source file for the given modules,
where it for each executable line is specified
how many times it has been executed.</p>
<p>The output file <c>OutFile</c> defaults to
<c>Module.COVER.out</c>, or <c>Module.COVER.html</c> if the
option <c>html</c> was used.</p>
<p>If <c>Modules</c> is an atom (one module), the return will
be <c>Answer</c>, else the return will be a
list, <c>{result,Ok,Fail}</c>.</p>
<p>If <c>Modules</c> is not given, all modules that have data
in the cover data table, are analysed. Note that this
includes both cover compiled modules and imported
modules.</p>
<p>If a module is not Cover compiled, this is indicated by the
error reason <c>{not_cover_compiled,Module}</c>.</p>
<p>If the source file and/or the output file cannot be opened using
<c>file:open/2</c>, the function returns
<c>{error,{file,File,Reason}}</c> where <c>File</c> is the file
name and <c>Reason</c> is the error reason.</p>
<p>If a module was cover compiled from the <c>.beam</c>
file, i.e. using <c>compile_beam/1</c> or
<c>compile_beam_directory/0,1</c>, it is assumed that the
source code can be found in the same directory as the
<c>.beam</c> file, in <c>../src</c> relative to that
directory, or using the source path in
<c>Module:module_info(compile)</c>. When using the latter,
two paths are examined: first the one constructed by
joining <c>../src</c> and the tail of the compiled path
below a trailing <c>src</c> component, then the compiled
path itself.
If no source code is found, this is indicated by the error reason
<c>{no_source_code_found,Module}</c>.</p>
</desc>
</func>
<func>
<name since="OTP R14B02">async_analyse_to_file(Module) -> </name>
<name since="OTP R14B02">async_analyse_to_file(Module,Options) -> </name>
<name since="OTP R14B02">async_analyse_to_file(Module, OutFile) -> </name>
<name since="OTP R14B02">async_analyse_to_file(Module, OutFile, Options) -> pid()</name>
<fsummary>Asynchronous call to analyse_to_file.</fsummary>
<type>
<v>Module = atom()</v>
<v>OutFile = string()</v>
<v>Options = [Option]</v>
<v>Option = html</v>
<v>Error = {not_cover_compiled,Module} | {file,File,Reason} | {no_source_code_found,Module} | not_main_node</v>
<v> File = string()</v>
<v> Reason = term()</v>
</type>
<desc>
<p>This function works exactly the same way as
<seealso marker="#analyse_to_file-1">analyse_to_file</seealso> except
that it is asynchronous instead of synchronous. The spawned process
will link with the caller when created. If an <c>Error</c> occurs
while doing the cover analysis the process will crash with the same
error reason as <seealso marker="#analyse_to_file-1">analyse_to_file</seealso>
would return.</p>
</desc>
</func>
<func>
<name>modules() -> [Module] | {error,not_main_node}</name>
<fsummary>Return all Cover compiled modules.</fsummary>
<type>
<v>Module = atom()</v>
</type>
<desc>
<p>Returns a list with all modules that are currently Cover
compiled.</p>
</desc>
</func>
<func>
<name>imported_modules() -> [Module] | {error,not_main_node}</name>
<fsummary>Return all modules for which there are imported data.</fsummary>
<type>
<v>Module = atom()</v>
</type>
<desc>
<p>Returns a list with all modules for which there are
imported data.</p>
</desc>
</func>
<func>
<name>imported() -> [File] | {error,not_main_node}</name>
<fsummary>Return all imported files.</fsummary>
<type>
<v>File = string()</v>
</type>
<desc>
<p>Returns a list with all imported files.</p>
</desc>
</func>
<func>
<name>which_nodes() -> [Node] | {error,not_main_node}</name>
<fsummary>Return all nodes that are part of the coverage analysis.</fsummary>
<type>
<v>Node = atom()</v>
</type>
<desc>
<p>Returns a list with all nodes that are part of the coverage
analysis. Note that the current node is not returned. This
node is always part of the analysis.</p>
</desc>
</func>
<func>
<name>is_compiled(Module) -> {file,File} | false | {error,not_main_node}</name>
<fsummary>Check if a module is Cover compiled.</fsummary>
<type>
<v>Module = atom()</v>
<v>Beam = string()</v>
</type>
<desc>
<p>Returns <c>{file,File}</c> if the module <c>Module</c> is
Cover compiled, or <c>false</c> otherwise. <c>File</c> is
the <c>.erl</c> file used by <c>cover:compile_module/1,2</c>
or the <c>.beam</c> file used by <c>compile_beam/1</c>.</p>
</desc>
</func>
<func>
<name>reset(Module) -></name>
<name>reset() -> ok | {error,not_main_node}</name>
<fsummary>Reset coverage data for Cover compiled modules.</fsummary>
<type>
<v>Module = atom()</v>
</type>
<desc>
<p>Resets all coverage data for a Cover compiled module
<c>Module</c> in the Cover database on all nodes. If the
argument is omitted, the coverage data will be reset for all
modules known by Cover.</p>
<p>If <c>Module</c> is not Cover compiled, the function returns
<c>{error,{not_cover_compiled,Module}}</c>.</p>
</desc>
</func>
<func>
<name>export(ExportFile)</name>
<name>export(ExportFile,Module) -> ok | {error,Reason}</name>
<fsummary>Reset coverage data for Cover compiled modules.</fsummary>
<type>
<v>ExportFile = string()</v>
<v>Module = atom()</v>
<v>Reason = {not_cover_compiled,Module} | {cant_open_file,ExportFile,Reason} | not_main_node</v>
</type>
<desc>
<p>Exports the current coverage data for <c>Module</c> to the
file <c>ExportFile</c>. It is recommended to name the
<c>ExportFile</c> with the extension <c>.coverdata</c>, since
other filenames can not be read by the web based interface to
cover.</p>
<p>If <c>Module</c> is not given, data for all Cover compiled
or earlier imported modules is exported.</p>
<p>This function is useful if coverage data from different
systems is to be merged.</p>
<p>See also <c>cover:import/1</c></p>
</desc>
</func>
<func>
<name>import(ExportFile) -> ok | {error,Reason}</name>
<fsummary>Reset coverage data for Cover compiled modules.</fsummary>
<type>
<v>ExportFile = string()</v>
<v>Reason = {cant_open_file,ExportFile,Reason} | not_main_node</v>
</type>
<desc>
<p>Imports coverage data from the file <c>ExportFile</c>
created with <c>cover:export/1,2</c>. Any analysis performed
after this will include the imported data.</p>
<p>Note that when compiling a module <em>all existing coverage data is removed</em>, including imported data. If a module is
already compiled when data is imported, the imported data is
<em>added</em> to the existing coverage data.</p>
<p>Coverage data from several export files can be imported
into one system. The coverage data is then added up when
analysing.</p>
<p>Coverage data for a module can not be imported from the
same file twice unless the module is first reset or
compiled. The check is based on the filename, so you can
easily fool the system by renaming your export file.</p>
<p>See also <c>cover:export/1,2</c></p>
</desc>
</func>
<func>
<name>stop() -> ok | {error,not_main_node}</name>
<fsummary>Stop Cover.</fsummary>
<desc>
<p>Stops the Cover server and unloads all Cover compiled code.</p>
</desc>
</func>
<func>
<name>stop(Nodes) -> ok | {error,not_main_node}</name>
<fsummary>Stop Cover on remote nodes.</fsummary>
<type>
<v>Nodes = [atom()]</v>
</type>
<desc>
<p>Stops the Cover server and unloads all Cover compiled code
on the given nodes. Data stored in the Cover database on the
remote nodes is fetched and stored on the main node.</p>
</desc>
</func>
<func>
<name since="OTP R16B">flush(Nodes) -> ok | {error,not_main_node}</name>
<fsummary>Collect cover data from remote nodes.</fsummary>
<type>
<v>Nodes = [atom()]</v>
</type>
<desc>
<p>Fetch data from the Cover database on the remote nodes and
stored on the main node.</p>
</desc>
</func>
</funcs>
<section>
<title>SEE ALSO</title>
<p>code(3), compile(3)</p>
</section>
</erlref>
